HUMAN EOSINOPHILS PREFERENTIALLY SURVIVE ON TISSUE FIBRONECTIN COMPARED WITH PLASMA FIBRONECTIN

Background Eosinophil-derived inflammatory mediators including cytokin es are considered to be important in the pathogenesis of allergic infl ammation. Fibronectin (Fn) has been shown to be a physiological trigge r of autocrine cytokine production by human eosinophils. Fn is encoded by a single gene, but alternate splicing of the primary RNA transcrip t results in polypeptide diversity in a cell type-specific fashion. Th us, tissue Fn contains approximately 50% more of the CS-1 cell binding region recognized by the integrin alpha 4 beta 1 compared with plasma Fn. Objective Since eosinophils are predominantly tissue-dwelling cel ls we compared the effect of tissue and plasma Fn on eosinophil surviv al in culture. Methods The viability and cytokine generation of eosino phils (>99.9% pure) cultured for up to 4 days in 96 well plates coated with tissue Fn, plasma Fn or BSA was compared. Results There was a si gnificant difference in the ability of tissue Fn to support eosinophil survival compared with plasma Fn (P < 0.01). Optimal survival with ti ssue Fn was seen at 25 mu g/well (70% +/- 2.0% viability at 3 days vs 7% +/- 2.2% viability on BSA). Significant (P < 0.001) cell viability on tissue Fn was observed for up to 4 days in culture (54% +/- 6.0%) c ompared with BSA coated wells. Addition of autologous mononuclear cell s (final concentration 0.5%, 1% or 2%) resulted in plasma Fn-dependent eosinophil survival comparable to that of 99.9% pure eosinophils adhe rent to tissue Fn. Tissue Fn-dependent survival was significantly inhi bited by anti-interleukin-3, anti-granulocyte macrophage colony stimul ating factor (GM-CSF) and anti-IL-5 monoclonal antibodies. Picogram qu antities of these three cytokines were detected in supernatants from e osinophils cultured for 3 days on tissue Fn using specific enzyme-link ed immunosorbent assays (ELISAs). Eosinophil survival on tissue Fn was significantly inhibited by anti-pr and alpha 4 beta 1 monoclonal anti body (MoAb) and also by a MoAb specific for the CS-1 motif in the IIIC S region of Fn. Conclusion These observations show preferential surviv al of eosinophils cultured on tissue Fn as a result of alpha 4 beta 1- dependent interaction with the CS-1 region of tissue Fn triggering aut ocrine cytokine synthesis and release, thereby promoting their surviva l and persistence within the tissues.